Allows for easy start by initially reducing crank compression, but once the engine starts and rpm increases, the compression release lobe is centrifugally retracted and the engine runs normally, with full compression, and without any loss in performanceDesigned as bolt-in cams for 103'' engine with stock 9.7:1 compression ratio up to 10.5:1More power across the rpm range best results from 2500 rpm - 5500 rpmIncludes camshafts, gearcover gasket, bearings, retaining ring, o-ring, threat lock and instructions Made in the USAWorks with stock, un-ported heads, but is great for S&S CNC ported heads.Installer must check coil bind, valve-to-valve clearance and valve-to-piston clearance.Not for models with OEM compression releases.